Why private conversion matters
Most converters upload your files to a server. Learn why browser-only conversion with ffmpeg.wasm is safer for personal and business videos.
Most online converters work the same way: you upload your video, it sits on someone else's server, gets converted, you download it, and you hope they delete it. That hope is not a privacy policy.
The real risk of server-side converters
When you upload a video or audio file, you are handing over content that may contain faces, voices, location data, financial discussions, or unreleased work. That file passes through:
- Upload logs and temporary storage
- Third-party cloud providers
- Analytics and ad trackers that log your IP and file name
- Backups that may persist longer than the "we delete after 1 hour" promise
Even if the service is honest, a breach, misconfigured bucket, or subpoena can expose your files. For creators handling client footage, lawyers handling depositions, or families sharing home videos, that risk is unacceptable.
How browser-only conversion works
JSM-Video.com does not have an upload endpoint. There is no server to receive your file. Instead, it loads ffmpeg.wasm - a WebAssembly port of FFmpeg - directly into your browser tab. Your file stays in your device memory, is written to the in-memory virtual file system of FFmpeg, converted, and offered back as a Blob for download.
We verify this with two technical choices:
- All conversion code runs in a Web Worker (
/ffmpeg/worker.js) isolated from the main thread. - Network inspector shows zero POST requests with your file. Only the engine (~30MB, cached after first use) is downloaded from a CDN.
When private conversion is essential
- Client work: Wedding videographers, YouTubers, agencies - you are under NDA. Local conversion keeps you compliant.
- Business recordings: Team meetings, interviews, HR recordings contain PII.
- Personal memories: Kids, home, travel. You don't want them on a random server.
Does private mean slower?
First load takes a moment because the engine downloads. After that, conversions run at near-native speed, and if your browser supports crossOriginIsolated, we enable multi-threaded mode that uses multiple CPU cores. For simple tasks like WAV export or MP4 to WebM via MediaRecorder, we even bypass FFmpeg entirely and use your GPU hardware acceleration for instant results.
How to stay private
- Check that the site says "No upload" and your DevTools Network tab shows no file upload.
- Prefer tools that are open about using ffmpeg.wasm or Canvas/WebCodecs locally.
- Close the tab after downloading - the virtual file system is wiped from RAM.
Private conversion is not a marketing badge. It is an architecture choice: no upload endpoint exists. That's how JSM-Video.com is built.